Waste heat boiler



'1. E.-BELL.

WASTE HEAT BOILER.

APPLICATION HLED FEB. 3. 1915.

1,332,284, Patented Mar. 2, 1920.

4 SHEETS-SHEET I.

WITNESSES: g g Y QQZZW v I. E. BELL.

WASTE HEAT BOILER.

APPLICATION FILED FEB. 3I I9I5.

1,332,284. PatentedMar. 2, 1920'.

-4 SHEETS-SHEET 2.

WITNESSES I I i I VENTOR.

r V r ATTORNEYS.

J. BELL.

WASTE HEAT BOILER.

APPLlCATlON FILED FEB-3.1915.

Patented Mar. 2, 1920.

4 SHEETS-SHEET 3- llllllllll /l/t 1 I I III],

a}? NVENTOR. BY

' J. E. BELL.

WASTE HEAT BOILER.

APPLICATION FILED FEB. a. 1915.

Patented Mar. 2, 1920.

4 SHEETS-SHEET 4 I "r I ////////////////////A7/I4l/l l/l/ y zi C NVENTOR. BY fi ATToRNEx s.

WITNESSES UNITED STATES PATENT onnron.

JOHN E. BELL, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE BABCOCK & WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A CORPORATION OF NEW JERSEY.

WASTE-HEAT BOILER.

Specification of Letters Patent.

Patented Mar.2, 1920.

Application filed February 3, 1915. Serial No. 5,833.

provements in \Vaste-Heat Boilers, of which the following is a specification.

My invention relates to waste heat boil ers; that is, boilers using the waste gases from furnaces, kilns, ovens, etc. It also re-v lates to combining a water tube boiler with a regenerative open-hearth furnace. In such combination there is no radiant heat on the tubes, such as is present in the ordinary coal-fired boilers. a. I

In the ordinary coal-fired boiler operated at rated capacity the weight of gas passing through the boiler per hour per square foot of average flowspace (average-area of the spaces between the tubes) is usually well under one thousand pounds. Such boilers use chimney draft and in order to reduce friction losses or draft drop through the boiler the flow spaces have been made relatively large.

I have discovered that I can obtain greatly increased efliciency by using a system of cross baflling which forces the waste gases across the tubes in a series of passes, and by arranging this baflling to give a relatively small area of flow space through these passes so as to greatly increase the velocity of the gases, and by using the suction fan to overcome the large draft loss, the heating surface of the'boiler being arranged in series in such a manner that, in connection with the added draft drop under the increased velocity, the desired draft will be afforded at the outlet of the furnace supplying the waste heat as well as at the gas out let of the boiler.

In my improved waste heat boiler when operated at rated capacity, the weight of gas passing through the boiler per hour per square foot of average flow area will be above two thousand pounds and may reach six or eight thousand pounds, the increased draft loss being overcome by the suction fan.

I find that in such a boiler the loss through the heavy draft drop is more than overcome by the increased absorption of heat so that while some power is lost in driving the suction fan, this loss is more than compensated forby the increased capacity and economy ofithe boiler.

In carrying out my invention in boilers of the so-called horizpntal type, I prefer to arrange the baffles at equal distances apart to give the minimum draft loss with the high velocity. For the same reason I prefer to arrange the bafliing so that the gases flow across the tubes at approximately right angles to their length, the alternate rows of tubes being so arranged that the axes of one horizontal row are in line with the spaces between the tubesof the adjacent rows. I also propose to use a fan so arranged that the air will pass through'it on a relatively smooth stream line, the fan being preferably of the centrifugal type with curvedblades, and the breeching connections between the boiler and the fan being arrangedto direct the flow of the gas without abrupt turns. In this way I reduce the frictional resistance as far as possible with the high velocity of gases employed, and can recover more of the waste heat than has heretofore been possible with waste heat boilers having a larger flow area and less draft drop;

In the drawings, in which I show a preferred form of my invention, Figure 1 shows a sectional side elevation of a Babcock & \Vilcox boiler arranged for waste heat, in accordance with my invention; Fig. 2 a vertical cross section on the line IIII of Fig. 1; Fig. 3 a diagrammatic cross section, partly in elevation, showing my waste heat boiler connected with a regenerative open-hearth furnace; Fig. 4 a detail section showing a damper in the bypass leading to the boiler; Fig. 5 a front'elevation'partly broken away showing one of the casings for a set of dusting openings; Fig. 6 a longitudinal section of the same; Fig. 7 a cross section of the same; and Fig. 8; a detail showing a portion of a closure for an access door.

Referring to Figs. 1 and 2 of these drawings, the boiler has an increased number of rows of tubes, 2 being the usual steam and water drums, 3 the front and 4 the rear water boxes, which in the form illustrated, are made up of sectional headers, 5 the lower set of tubes, and 6 the upper set of tubes. These tubes are arranged in a genends being connected into the headers in the usual manner and the headers connected to the steam and water drums as shown at 7 and 8. 9 represents two vertical transverse bafiles which, as shown, are spaced substantially equally distant from each other and from the headers so as to give three transverse passes, each having substantially the same sectional area. Preferably the battles are parallel with the water boxes?) and a. The flow spaces in these passes are much smaller in proportion to the amount of gases than those'in ordinary boilers, giving a relatively heavy draft dr'op. IO-represents the inlet port for the waste gases which rise through the first vertical pass, sweep over the su Jerheater shown at 11, if such is used, then escend through the middle pass and rise through the last pass to the outlet breec'hing l2surroundin'g the rear parts of the steam and water drums. 13 is a sue tion fan which is connected to the outlet to induce the necessary 'draft'to overcome the heavy draftloss in pulling the relatively large amount of gases'through the relatively small passages over-the heating surface.

In connecting this; boiler to a regenerative open-hearth furnace I preferably connectthe-- inlet port- 10 to abypass flue 14:, such as shown in Fig. 3, leading from the stack' flue 15 of the open-hearth furnace. In this figure, 16 represents the open-hearth furnace, 17 the gas and air regenerators which are connected through suitable reversing valves with the air, gas and stack flues. 18 is a damper by which direct 'conneztion between the furnace stack flue and the stack 19 may be cut off, and 20 is a similar damper controlling the inflow of waste gases to the boiler.

After the gases have been drawn through the fan 13 they pass through a branch flue 21 into the stack, this flue preferably having a control damper, as shown at 22, Fig. 1.

In the breeching 12 leading to the fan inlet I preferably provide the curved vane 23 and 24 to give the smooth stream lines leadifng to the curved blades of the centrifugal In this boiler there will be a considerable sub-atmosphere within the boiler setting and to maintain this sub-atmosphere I make the boiler casing as tight as possible, the various openings into it being preferably provided with gaskets or otherwise sealed as far as possible against the entrance of air.

As the bafiles are vertical, they afford no resting place for the dust and soot with which waste gases are usually laden, sometimes in great quantities. ,It is also important to provide openings through which an air or steam lance may be inserted to remove the soot and dust which collects on the tubes, These openings are shown at 26 and in addition to the ordinary closure therefore I preferably provide an additional gasket inclosure 29 which will serve to additionally seal theseopeuings when not in use.

The cleaning doors are preferably of the explosion type, and asbestos-packed closing doors are provided over these cleaning doors.

In the use of the boiler a large weight of waste gases is staked through the. three transverse passes by means of the suction fan, and while there is a heavy draft loss owing the high velocity and the relatively small area of passageways compared with the weight of the gases, yet this is overcome by the suction fan. The power lost in driving is more than overcome by the larger amount of power generated from thewaste heat.

It will be noted that the cross sectional area of the several passes is substantially the same, and this is important asit aids in reducing the draft drop over the gases in such waste heat boilers where there is no radiant heat directly from the fire acting on ,the tubes.

It will be noted that in my preferred form which I have illustrated, the number of horizontal rows of boiler tubes is much greater than in direct fired practice, there being twenty-six rows shown, which will afford seventy-eight contacts between the gases and the rows of tubes in the three vertical passes shown, before the gases reach the boiler outlet. these passes, measured in rows of tubes, is therefore abnormally great, with a corresponding draft drop. While this great number of contacts is desirable, it is'not necessary to have it as large as illustrated, but I The combined length of find that to obtain the best results, there i should be at least forty-eight successive contacts between the gases and rows of tubes, such contacts being distributed in at least three passes.

Heretofore with waste gases having a temperature of say 1000 F. the recovery of power obtained by subjecting a boiler to these gases was not sufiicient to warrant the investment. IVith my improvedboiler, however, the larger amount of power obtained more than compensates for the cost of installation and the cost of operating, and this is due to the peculiar combination as above described.

In the combined regenerative open-hearth and waste heat boiler structure the waste gases, after passing through one set of regenerators, enter the stack flue and flow through the bypass flue 1:: into the inlet port sucked and pass to the stack. The dampers 1.8 and 20 are used to control the draft to the boiler and the stack, and to shut oil the boiler and give the direct connection to the stack, when desired.

In Figs. 5, (3 and 7 I show an arrangement 10 of the boiler through which they are of the dusting openings in which 25 is the general casing set in the brickwork and having the dusting openings 26 therein for admission of a steam lance. The outer surfaces of these openings are preferabl inclined as shown, and provided with sliding shutters 27 which slide within brackets 28.

In order to more efiectually seal these dusting openings and make the setting approximately airtight I provide an additional closing door 29 hinged to the casing 25 at 30, and provided at its edge with a rounding gasket 31 which seats against the outer surrounding edge portion of the casing 25.

In Fig. 8 I show a small detail portion of an access door for admission to the setting in which 32 is a portion of the door having gasket 33 seating against the edge portion of the gasket 84 in which the access opening is formed.

The advantages of my invention result from a coordination between the volume of the waste gases passing through the boiler, the direction and dimensions of the boiler passes, the number and direction of tube contacts in the passes, and the suction, whereby a balance is maintained between the draft at the outlet of the furnace supplying the waste gases and at the boileroutlet. This coordination is contributed to and efliciently applied by the construction of the boiler shown, wherein the passes back and forth across the tubes are produced by batlles extending substantially parallel with the vertically extending headers or water boxes constituting the front and rear of the boiler, and connected by the straight inclined water tubes across which the passes extend. I believe that I am the first to discover the advantages due to this peculiar combination wherein the high velocity of gases gives somuch increased power as to more than offset the work of the power lost in driving the fan; and to warrant installation oi waste heat boilers in places where heretofore such heat could not be commercially utilized.

hat I claim and desire to secure by Letters Patent of the United States is 1. The method of operating waste heat boilers consisting in drawing the waste gases from an industrial furnace successively through a plurality of passes across the tubes or a water tube boiler and imparting substantially all of the heat from said waste heat gases to said tubes by convection, with a. velocity and draft loss such that when sufficient waste heat gases are supplied to operate the boiler at or about its rated capacity the average weight of the gases drawn per hour per square foot of average flow area is at least 2,000 pounds, substantially as described.

2. The method of operating waste heat boilers consisting in drawing the waste gases from an industrial furnace successively through a plurality of passes of substantially equal cross sectional area across the tubes of a water tube boiler and imparting wholly by convection from the waste heat gases, said boiler having balfies arranged to conduct the gases transversely of the tubes, and an induction device arranged to draw the waste gases through said cross passes over the tubes at such a rate that the average weight of gases drawn per square foot of average flow space at or about rated capacity is at least two thousand pounds per hour.

4,. A waste heat boiler in which the heat is transferred to the tubes substantially wholly by convection from the waste heat gases, said boiler having baflles arranged to conduct the gases transversely of the tubes, the

passes being of substantially equal cross sectional area and the water tubes being staggered, and an induction device arranged to draw the waste gases through said cross passes over the tubes at such a rate that the average weight of gases drawn per square foot of average flow space at or about rated gapacity is at least two thousand pounds per our.

5. A waste heat boiler having battles arranged in a transverse direction to the tubes for conducting the gases several times over each of the tubes oi the main bank, an induced draft apparatus connected to the flue outlet of the boiler and arranged to draw the waste gases through said cross passes over the tubes at such a rate that the average weight of gases drawn per square foot of average flow space at or about the rater capacity is at least two thousand, pounds per hour, and a casing for the boiler having access openings provided with substantially air-tight closures.

6. A waste heat boiler having battling arran ed to give the gases successive back and forth asses across the same tubes, the boiler casing being substantially air-tight and having dusting openings provided with substantially air-tight closures, and a suction fan arranged to draw said gases over the heating surface, the bafl'ling and water hea ing surface being so arranged that the aver age weight of the gases drawn per hour per square foot of average flow area is at least 2,000 pounds, substantially as described.

-7. A waste heat boiler having tubes. pro vided with 'cross *bafiiing givi'n' the waste gases a: plurality" of back and 'forth passes across the tubes, a by-pass flue leading from 1 an industrial furnace flue to the boiler and 8. A wasteheat boiler'having bafiles ar-.

ranged in 'a transverse direction to the tubes forrat'ssing gases up and down over the water tubes, the last pass of the gases being upward; an outlet flue leading upward from the boiler to a stack, and an induced draft apparatus mounted above the boiler and connected to the last pass of the boiler for conducting gases therein to the outlet hue, substantially as'described.

9. The combination with an industrial furnace 'of' a branch flue leading from the outlet flu'e'thereof' to a watertube boiler, the boiler lntviugcross baffling giving the a pluralityv of back andx'forth p'lasses'across thetu bes, ands: suction fan arranged to draw the waste gases through the boiler, the fan inconj'nncti'on with the'tubes and baffling being so arranged that the aver age weight of gases per hour per square foot of average flow space is at least 2,000 und's, the last "for the gases in the bg iler being upward, and an outlet flue leading from the said upward passto a stack and"'containing. the fan, said fan being mouli lid above 'the boiler setting, substantially'as describedl 10. The combination with an industrial furnace,fof a waste heat water tube boiler, a flue arrangedito' lead the waste gases from the industrial'furnace to the boiler, and a suction device arranged to suck the waste gases through the industrial furnace and through the boiler at such a. rate that the average weight of gases drawn per square foot of average flow space at or about rat-ed capacityiis at least two thousand pounds per hour, the heating surface of the boiler being arranged in ser es in such manner that in connection with the added draft drop under the increased velocity, the desired draft will be afforded at the outlet of the industrial furnace and the outlet offthe boiler.

11. The combination with. an industrial furnace having a flue for waste gases, of a water tube boiler set in the waste-flue and having cross baffling arrangedto give the waste gases a plurality of back and forth passes across the tubes, and a suction device arranged to suck the waste, gases through the industrial furnace and through the boiler at surh a rate thatthe average weight of gases drawn per square foot of average flow space at or about rated capacity is at least two thousand pounds per hour, the heating surface of the boiler beingarranged'inseries in-such manner that in connection with the added draft drop under increased velocity the desired draft will be afforded at the'out let of the industrial furnace and the outlet of the boiler. a

12. The combination with an industrial furnace having a fine for waste gases'yof a water tube boiler set in the waste fine and having vertically extending water boxes conincreased velocity the desired draft wi'll' lbe afi'orded'at the outlet of theindustriaI-fin' nace and" the outlet of the boiler i 13. The combination with an industrial furnace having a flue for waste gases, l of a water tube boiler set in the waste flueand having vertically extending water boxes connected by rows of horizontally inclined straight tubes and having cross'ba'filing ar ranged togive the gases a plurality ofback and forth passes across the tubes and substantially parallel with the. water boxes, said tubes and said baffling being constructed and arranged so that the gases passingthrough the boiler will contact with; at least forty-eight rows of tube sections distributed in at least three passes, and a suction device arranged to suck the waste gases through the industrial furnace and through the boiler, the heating surface of the boiler being arranged in series in such manner that in connection with the added draft drop under the velocity imparted by the suction device, the desired draft will-be afforded at the outlet of the industrial furnace and the outlet of the boiler.

14. The combination.with an industrial furnace having a flue for waste gases,ofasections distributed in at least' three passes, and a suction device arranged to suck the waste gases through the industrial furnace and through the boiler at such a rate that the average weight of gases drawn per square foot of average flow space at or about rated capacity is at least two thousand pounds per hour, the heatingsurface of the boiler being arranged in series in such manner that in connection with the added draft drop under increased velocity the desired draft will be afforded at the outlet of the in dustrial furnace and the outlet of the boiler.

15. A waste heat boiler in which the heat is transferred to the tubes substantially wholly by convection from the waste gases, said boiler having vertically extending water boxes connected by rows of horizontally inclined straight tubes and having cross baflling arranged to give the gases a plurality of back and forth passes across the tubes and substantially parallel with the water boxes, and asuction device arranged to suck the gases through the boiler at such. a rate that the average weight of gases drawn per square foot of average flow space at or about the rated capacity is at least two thousand pounds per hour.

16. A waste heat boiler in which the heat is transferred to the tubes substantially wholly by convection from the waste gases, said boiler having vertically extending water boxes connected by rows of horizontally inclined straight tubes and having cross baffling arranged to give the gases a plurality of back and forth passes across the tubes and substantially parallel with the water boxes, said passes being of substantially equal cross sectional area, and a suction device arranged to suck the gases through the boiler at such a rate that the average weight of gases drawn per square foot of average flow space at or about the rated capacity is at least two thousand pounds per hour.

17. A waste heat boiler in which the heat is transferred to the tubes substantially wholly by convection from the waste gases, said boiler having vertically extending water boxes connected by rows of horizontally inclined straight tubes and having cross baffling arranged to give the gases a plurality of back and forth passes across the tubes and substantially parallel with the water boxes, and a suction device arranged to suck the gases through the boiler at, such a rate that the average weight of gases drawn per square foot of average flow space at or about the rated capacity is at least two thousand pounds per hour, said tubes and said baflling being constructed and arranged so that the gases passing through the boiler will contact with at least forty-eight rows of tube sections distributed in at least three passes.

18. The combination with an industrial furnace having a flue for waste gases, of a water tube boiler set in the waste flue and having vertically extending water boxes connected by rows of horizontally inclined straight tubes, the tubes in successive rows being staggered, and having cross battling arranged to give the gases a plurality of back and forth passes across the tubes and substantially parallel with the water boxes, said passes being of substantially equal cross sectional area, and a suction device arranged to suck the waste gases through the industrial furnace and through the boiler, the heating surface of the boiler being .arranged in series'in such manner that in connection with the added draft drop under the velocity imparted by the suction device the desired draft will be afforded at the outlet of the industrial furnace and the outlet of the boiler.

In testimony whereof I have hereunto signed my name in the presence of two subscribing witnesses.

JOHN E. BELL. 

